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//! This is a base16 (e.g. hexadecimal) encoding and decoding library with an //! emphasis on performance. The API is very similar and inspired by the base64 //! crate's API, however it's less complex (base16 is much more simple than //! base64). //! //! # Encoding //! //! The config options at the moment are limited to the output case (upper vs //! lower). //! //! | Function | Output | Allocates | Requires `alloc` feature | //! | ---------------------------------- | ---------------------------- | ----------------------- | ------------------------ | //! | [`encode_upper`], [`encode_lower`] | Returns a new `String` | Always | Yes | //! | [`encode_config`] | Returns a new `String` | Always | Yes | //! | [`encode_config_buf`] | Appends to provided `String` | If buffer needs to grow | Yes | //! | [`encode_config_slice`] | Writes to provided `&[u8]` | Never | No | //! //! # Decoding //! //! Note that there are no config options (In the future one might be added to //! restrict the input character set, but it's not clear to me that this is //! useful). //! //! | Function | Output | Allocates | Requires `alloc` feature | //! | ----------------- | ----------------------------- | ----------------------- | ------------------------ | //! | [`decode`] | Returns a new `Vec<u8>` | Always | Yes | //! | [`decode_slice`] | Writes to provided `&[u8]` | Never | No | //! | [`decode_buf`] | Appends to provided `Vec<u8>` | If buffer needs to grow | Yes | //! //! # Features //! //! This crate has two features, both are enabled by default and exist to allow //! users in `no_std` environments to disable various portions of . //! //! - The `"alloc"` feature, which is on by default, adds a number of helpful //! functions that require use of the [`alloc`][alloc_crate] crate, but not the //! rest of `std`. //! - This is `no_std` compatible. //! - Each function should list whether or not it requires this feature //! under the `Availability` of its documentation. //! //! - The `"std"` feature, which is on by default, enables the `"alloc"` //! feature, and additionally makes [`DecodeError`] implement the //! `std::error::Error` trait. //! //! - Frustratingly, this trait is in `std` (and not in `core` or `alloc`), //! but not implementing it would be quite annoying for some users, so //! it's kept, even though it's what prevents us from being `no_std` //! compatible in all configurations. //! //! [alloc_crate]: https://doc.rust-lang.org/alloc/index.html #![cfg_attr(not(feature = "std"), no_std)] #![deny(missing_docs)] #[cfg(feature = "alloc")] extern crate alloc; #[cfg(feature = "alloc")] use alloc::{vec::Vec, string::String}; /// Configuration options for encoding. Just specifies whether or not output /// should be uppercase or lowercase. #[derive(Debug, Clone, Copy, Eq, PartialEq, Ord, PartialOrd, Hash)] pub enum EncConfig { /// Encode using lower case characters for hex values >= 10 EncodeLower, /// Encode using upper case characters for hex values >= 10 EncodeUpper, } pub use EncConfig::*; #[inline] fn encoded_size(source_len: usize) -> usize { const USIZE_TOP_BIT: usize = 1usize << (core::mem::size_of::<usize>() * 8 - 1); if (source_len & USIZE_TOP_BIT) != 0 { usize_overflow(source_len) } source_len << 1 } #[inline] fn encode_slice_raw(src: &[u8], cfg: EncConfig, dst: &mut [u8]) { let lut = if cfg == EncodeLower { HEX_LOWER } else { HEX_UPPER }; debug_assert!(dst.len() == encoded_size(src.len())); dst.chunks_exact_mut(2).zip(src.iter().copied()).for_each(|(d, sb)| { d[0] = lut[(sb >> 4) as usize]; d[1] = lut[(sb & 0xf) as usize]; }) } #[cfg(feature = "alloc")] #[inline] fn encode_to_string(bytes: &[u8], cfg: EncConfig) -> String { let size = encoded_size(bytes.len()); let mut buf: Vec<u8> = Vec::with_capacity(size); unsafe { buf.set_len(size); } encode_slice_raw(bytes, cfg, &mut buf); debug_assert!(core::str::from_utf8(&buf).is_ok()); unsafe { String::from_utf8_unchecked(buf) } } #[cfg(feature = "alloc")] #[inline] unsafe fn grow_vec_uninitialized(v: &mut Vec<u8>, grow_by: usize) -> usize { v.reserve(grow_by); let initial_len = v.len(); let new_len = initial_len + grow_by; debug_assert!(new_len <= v.capacity()); v.set_len(new_len); initial_len } /// Encode bytes as base16, using lower case characters for nibbles between 10 /// and 15 (`a` through `f`). /// /// This is equivalent to `base16::encode_config(bytes, base16::EncodeUpper)`. /// /// # Example /// /// ``` /// assert_eq!(base16::encode_lower(b"Hello World"), "48656c6c6f20576f726c64"); /// assert_eq!(base16::encode_lower(&[0xff, 0xcc, 0xaa]), "ffccaa"); /// ``` /// /// # Availability /// /// This function is only available when the `alloc` feature is enabled, as it /// needs to produce a String. #[cfg(feature = "alloc")] #[inline] pub fn encode_lower<T: ?Sized + AsRef<[u8]>>(input: &T) -> String { encode_to_string(input.as_ref(), EncodeLower) } /// Encode bytes as base16, using upper case characters for nibbles between /// 10 and 15 (`A` through `F`). /// /// This is equivalent to `base16::encode_config(bytes, base16::EncodeUpper)`. /// /// # Example /// /// ``` /// assert_eq!(base16::encode_upper(b"Hello World"), "48656C6C6F20576F726C64"); /// assert_eq!(base16::encode_upper(&[0xff, 0xcc, 0xaa]), "FFCCAA"); /// ``` /// /// # Availability /// /// This function is only available when the `alloc` feature is enabled, as it /// needs to produce a `String`. #[cfg(feature = "alloc")] #[inline] pub fn encode_upper<T: ?Sized + AsRef<[u8]>>(input: &T) -> String { encode_to_string(input.as_ref(), EncodeUpper) } /// Encode `input` into a string using the listed config. The resulting string /// contains `input.len() * 2` bytes. /// /// # Example /// /// ``` /// let data = [1, 2, 3, 0xaa, 0xbb, 0xcc]; /// assert_eq!(base16::encode_config(&data, base16::EncodeLower), "010203aabbcc"); /// assert_eq!(base16::encode_config(&data, base16::EncodeUpper), "010203AABBCC"); /// ``` /// /// # Availability /// /// This function is only available when the `alloc` feature is enabled, as it /// needs to produce a `String`. #[cfg(feature = "alloc")] #[inline] pub fn encode_config<T: ?Sized + AsRef<[u8]>>(input: &T, cfg: EncConfig) -> String { encode_to_string(input.as_ref(), cfg) } /// Encode `input` into the end of the provided buffer. Returns the number of /// bytes that were written. /// /// Only allocates when `dst.size() + (input.len() * 2) >= dst.capacity()`. /// /// # Example /// /// ``` /// let messages = &["Taako, ", "Merle, ", "Magnus"]; /// let mut buffer = String::new(); /// for msg in messages { /// let bytes_written = base16::encode_config_buf(msg.as_bytes(), /// base16::EncodeUpper, /// &mut buffer); /// assert_eq!(bytes_written, msg.len() * 2); /// } /// assert_eq!(buffer, "5461616B6F2C204D65726C652C204D61676E7573"); /// ``` /// # Availability /// /// This function is only available when the `alloc` feature is enabled, as it /// needs write to a `String`. #[cfg(feature = "alloc")] #[inline] pub fn encode_config_buf<T: ?Sized + AsRef<[u8]>>(input: &T, cfg: EncConfig, dst: &mut String) -> usize { let src = input.as_ref(); let bytes_to_write = encoded_size(src.len()); // Swap the string out while we work on it, so that if we panic, we don't // leave behind garbage (we do clear the string if we panic, but that's // better than UB) let mut buf = core::mem::replace(dst, String::new()).into_bytes(); let cur_size = unsafe { grow_vec_uninitialized(&mut buf, bytes_to_write) }; encode_slice_raw(src, cfg, &mut buf[cur_size..]); debug_assert!(core::str::from_utf8(&buf).is_ok()); // Put `buf` back into `dst`. *dst = unsafe { String::from_utf8_unchecked(buf) }; bytes_to_write } /// Write bytes as base16 into the provided output buffer. Never allocates. /// /// This is useful if you wish to avoid allocation entirely (e.g. your /// destination buffer is on the stack), or control it precisely. /// /// # Panics /// /// Panics if the desination buffer is insufficiently large. /// /// # Example /// /// ``` /// # extern crate core as std; /// // Writing to a statically sized buffer on the stack. /// let message = b"Wu-Tang Killa Bees"; /// let mut buffer = [0u8; 1024]; /// /// let wrote = base16::encode_config_slice(message, /// base16::EncodeLower, /// &mut buffer); /// /// assert_eq!(message.len() * 2, wrote); /// assert_eq!(std::str::from_utf8(&buffer[..wrote]).unwrap(), /// "57752d54616e67204b696c6c612042656573"); /// /// // Appending to an existing buffer is possible too. /// let wrote2 = base16::encode_config_slice(b": The Swarm", /// base16::EncodeLower, /// &mut buffer[wrote..]); /// let write_end = wrote + wrote2; /// assert_eq!(std::str::from_utf8(&buffer[..write_end]).unwrap(), /// "57752d54616e67204b696c6c6120426565733a2054686520537761726d"); /// ``` /// # Availability /// /// This function is available whether or not the `alloc` feature is enabled. #[inline] pub fn encode_config_slice<T: ?Sized + AsRef<[u8]>>(input: &T, cfg: EncConfig, dst: &mut [u8]) -> usize { let src = input.as_ref(); let need_size = encoded_size(src.len()); if dst.len() < need_size { dest_too_small_enc(dst.len(), need_size); } encode_slice_raw(src, cfg, &mut dst[..need_size]); need_size } /// Encode a single character as hex, returning a tuple containing the two /// encoded bytes in big-endian order -- the order the characters would be in /// when written out (e.g. the top nibble is the first item in the tuple) /// /// # Example /// ``` /// assert_eq!(base16::encode_byte(0xff, base16::EncodeLower), [b'f', b'f']); /// assert_eq!(base16::encode_byte(0xa0, base16::EncodeUpper), [b'A', b'0']); /// assert_eq!(base16::encode_byte(3, base16::EncodeUpper), [b'0', b'3']); /// ``` /// # Availability /// /// This function is available whether or not the `alloc` feature is enabled. #[inline] pub fn encode_byte(byte: u8, cfg: EncConfig) -> [u8; 2] { let lut = if cfg == EncodeLower { HEX_LOWER } else { HEX_UPPER }; let lo = lut[(byte & 15) as usize]; let hi = lut[(byte >> 4) as usize]; [hi, lo] } /// Convenience wrapper for `base16::encode_byte(byte, base16::EncodeLower)` /// /// See also `base16::encode_byte_u`. /// /// # Example /// ``` /// assert_eq!(base16::encode_byte_l(0xff), [b'f', b'f']); /// assert_eq!(base16::encode_byte_l(30), [b'1', b'e']); /// assert_eq!(base16::encode_byte_l(0x2d), [b'2', b'd']); /// ``` /// # Availability /// /// This function is available whether or not the `alloc` feature is enabled. #[inline] pub fn encode_byte_l(byte: u8) -> [u8; 2] { encode_byte(byte, EncodeLower) } /// Convenience wrapper for `base16::encode_byte(byte, base16::EncodeUpper)` /// /// See also `base16::encode_byte_l`. /// /// # Example /// ``` /// assert_eq!(base16::encode_byte_u(0xff), [b'F', b'F']); /// assert_eq!(base16::encode_byte_u(30), [b'1', b'E']); /// assert_eq!(base16::encode_byte_u(0x2d), [b'2', b'D']); /// ``` /// # Availability /// /// This function is available whether or not the `alloc` feature is enabled. #[inline] pub fn encode_byte_u(byte: u8) -> [u8; 2] { encode_byte(byte, EncodeUpper) } /// Represents a problem with the data we want to decode. /// /// This implements `std::error::Error` and `Display` if the `std` /// feature is enabled, but only `Display` if it is not. #[derive(Debug, PartialEq, Eq, Clone)] pub enum DecodeError { /// An invalid byte was found in the input (bytes must be `[0-9a-fA-F]`) InvalidByte { /// The index at which the problematic byte was found. index: usize, /// The byte that we cannot decode. byte: u8 }, /// The length of the input not a multiple of two InvalidLength { /// The input length. length: usize }, } #[cold] fn invalid_length(length: usize) -> DecodeError { DecodeError::InvalidLength { length } } #[cold] fn invalid_byte(index: usize, src: &[u8]) -> DecodeError { DecodeError::InvalidByte { index, byte: src[index] } } impl core::fmt::Display for DecodeError { fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result { match *self { DecodeError::InvalidByte { index, byte } => { write!(f, "Invalid byte `b{:?}`, at index {}.", byte as char, index) } DecodeError::InvalidLength { length } => write!(f, "Base16 data cannot have length {} (must be even)", length), } } } #[cfg(feature = "std")] impl std::error::Error for DecodeError { fn description(&self) -> &str { match *self { DecodeError::InvalidByte { .. } => "Illegal byte in base16 data", DecodeError::InvalidLength { .. } => "Illegal length for base16 data", } } fn cause(&self) -> Option<&dyn std::error::Error> { None } } #[inline] fn decode_slice_raw(src: &[u8], dst: &mut[u8]) -> Result<(), usize> { // checked in caller. debug_assert!(src.len() / 2 == dst.len()); debug_assert!((src.len() & 1) == 0); src.chunks_exact(2).enumerate().zip(dst.iter_mut()).try_for_each(|((si, s), d)| { let r0 = DECODE_LUT[s[0] as usize]; let r1 = DECODE_LUT[s[1] as usize]; if (r0 | r1) >= 0 { *d = ((r0 << 4) | r1) as u8; Ok(()) } else { Err(si * 2) } }).map_err(|bad_idx| raw_decode_err(bad_idx, src)) } #[cold] #[inline(never)] fn raw_decode_err(idx: usize, src: &[u8]) -> usize { let b0 = src[idx]; if decode_byte(b0).is_none() { idx } else { idx + 1 } } /// Decode bytes from base16, and return a new `Vec<u8>` containing the results. /// /// # Example /// /// ``` /// assert_eq!(&base16::decode("48656c6c6f20576f726c64".as_bytes()).unwrap(), /// b"Hello World"); /// assert_eq!(&base16::decode(b"deadBEEF").unwrap(), /// &[0xde, 0xad, 0xbe, 0xef]); /// // Error cases: /// assert_eq!(base16::decode(b"Not Hexadecimal!"), /// Err(base16::DecodeError::InvalidByte { byte: b'N', index: 0 })); /// assert_eq!(base16::decode(b"a"), /// Err(base16::DecodeError::InvalidLength { length: 1 })); /// ``` /// # Availability /// /// This function is only available when the `alloc` feature is enabled, as it /// needs to produce a Vec. #[cfg(feature = "alloc")] #[inline] pub fn decode<T: ?Sized + AsRef<[u8]>>(input: &T) -> Result<Vec<u8>, DecodeError> { let src = input.as_ref(); if (src.len() & 1) != 0 { return Err(invalid_length(src.len())); } let need_size = src.len() >> 1; let mut dst = Vec::with_capacity(need_size); unsafe { dst.set_len(need_size); } match decode_slice_raw(src, &mut dst) { Ok(()) => Ok(dst), Err(index) => Err(invalid_byte(index, src)) } } /// Decode bytes from base16, and appends into the provided buffer. Only /// allocates if the buffer could not fit the data. Returns the number of bytes /// written. /// /// In the case of an error, the buffer should remain the same size. /// /// # Example /// /// ``` /// # extern crate core as std; /// # extern crate alloc; /// # use alloc::vec::Vec; /// let mut result = Vec::new(); /// assert_eq!(base16::decode_buf(b"4d61646f6b61", &mut result).unwrap(), 6); /// assert_eq!(base16::decode_buf(b"486F6D757261", &mut result).unwrap(), 6); /// assert_eq!(std::str::from_utf8(&result).unwrap(), "MadokaHomura"); /// ``` /// # Availability /// /// This function is only available when the `alloc` feature is enabled, as it /// needs to write to a Vec. #[cfg(feature = "alloc")] #[inline] pub fn decode_buf<T: ?Sized + AsRef<[u8]>>(input: &T, v: &mut Vec<u8>) -> Result<usize, DecodeError> { let src = input.as_ref(); if (src.len() & 1) != 0 { return Err(invalid_length(src.len())); } // Swap the vec out while we work on it, so that if we panic, we don't leave // behind garbage (this will end up cleared if we panic, but that's better // than UB) let mut work = core::mem::replace(v, Vec::default()); let need_size = src.len() >> 1; let current_size = unsafe { grow_vec_uninitialized(&mut work, need_size) }; match decode_slice_raw(src, &mut work[current_size..]) { Ok(()) => { // Swap back core::mem::swap(v, &mut work); Ok(need_size) } Err(index) => { work.truncate(current_size); // Swap back core::mem::swap(v, &mut work); Err(invalid_byte(index, src)) } } } /// Decode bytes from base16, and write into the provided buffer. Never /// allocates. /// /// In the case of a decoder error, the output is not specified, but in practice /// will remain untouched for an `InvalidLength` error, and will contain the /// decoded input up to the problem byte in the case of an InvalidByte error. /// /// # Panics /// /// Panics if the provided buffer is not large enough for the input. /// /// # Example /// ``` /// let msg = "476f6f642072757374206c6962726172696573207573652073696c6c79206578616d706c6573"; /// let mut buf = [0u8; 1024]; /// assert_eq!(base16::decode_slice(&msg[..], &mut buf).unwrap(), 38); /// assert_eq!(&buf[..38], b"Good rust libraries use silly examples".as_ref()); /// /// let msg2 = b"2E20416C736F2C20616E696D65207265666572656e636573"; /// assert_eq!(base16::decode_slice(&msg2[..], &mut buf[38..]).unwrap(), 24); /// assert_eq!(&buf[38..62], b". Also, anime references".as_ref()); /// ``` /// # Availability /// /// This function is available whether or not the `alloc` feature is enabled. #[inline] pub fn decode_slice<T: ?Sized + AsRef<[u8]>>(input: &T, out: &mut [u8]) -> Result<usize, DecodeError> { let src = input.as_ref(); if (src.len() & 1) != 0 { return Err(invalid_length(src.len())); } let need_size = src.len() >> 1; if out.len() < need_size { dest_too_small_dec(out.len(), need_size); } match decode_slice_raw(src, &mut out[..need_size]) { Ok(()) => Ok(need_size), Err(index) => Err(invalid_byte(index, src)) } } /// Decode a single character as hex. /// /// Returns `None` for values outside the ASCII hex range. /// /// # Example /// ``` /// assert_eq!(base16::decode_byte(b'a'), Some(10)); /// assert_eq!(base16::decode_byte(b'B'), Some(11)); /// assert_eq!(base16::decode_byte(b'0'), Some(0)); /// assert_eq!(base16::decode_byte(b'q'), None); /// assert_eq!(base16::decode_byte(b'x'), None); /// ``` /// # Availability /// /// This function is available whether or not the `alloc` feature is enabled. #[inline] pub fn decode_byte(c: u8) -> Option<u8> { if c.wrapping_sub(b'0') <= 9 { Some(c.wrapping_sub(b'0')) } else if c.wrapping_sub(b'a') < 6 { Some(c.wrapping_sub(b'a') + 10) } else if c.wrapping_sub(b'A') < 6 { Some(c.wrapping_sub(b'A') + 10) } else { None } } static HEX_UPPER: [u8; 16] = *b"0123456789ABCDEF"; static HEX_LOWER: [u8; 16] = *b"0123456789abcdef"; static DECODE_LUT: [i8; 256] = [ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, -1, -1, -1, -1, -1, -1, -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1 ]; // Outlined assertions. #[inline(never)] #[cold] fn usize_overflow(len: usize) -> ! { panic!("usize overflow when computing size of destination: {}", len); } #[cold] #[inline(never)] fn dest_too_small_enc(dst_len: usize, need_size: usize) -> ! { panic!("Destination is not large enough to encode input: {} < {}", dst_len, need_size); } #[cold] #[inline(never)] fn dest_too_small_dec(dst_len: usize, need_size: usize) -> ! { panic!("Destination buffer not large enough for decoded input {} < {}", dst_len, need_size); } // encoded_size smoke tests #[cfg(test)] mod tests { use super::*; #[test] #[should_panic] #[cfg(pointer_size )] fn test_encoded_size_panic_top_bit() { #[cfg(target_pointer_width = "64")] let usz = 0x8000_0000_0000_0000usize; #[cfg(target_pointer_width = "32")] let usz = 0x8000_0000usize; let _ = encoded_size(usz); } #[test] #[should_panic] fn test_encoded_size_panic_max() { let _ = encoded_size(usize::max_value()); } #[test] fn test_encoded_size_allows_almost_max() { #[cfg(target_pointer_width = "64")] let usz = 0x7fff_ffff_ffff_ffffusize; #[cfg(target_pointer_width = "32")] let usz = 0x7fff_ffffusize; assert_eq!(encoded_size(usz), usz * 2); } }